1. Field of the Invention
This invention relates to a reverse-conducting gate turn-off (GTO) thyristor for high current and high voltage switching applications.
2. Discussion of Background
Such a semiconductor component as above noted is described in Swiss Patent Specification No. 594,989. In this document, a reverse-conducting thyristor is specified which combines a thyristor and an antiparallel diode on one silicon disk. Special protective rings in the component prevent the two components from mutually influencing each other.
Such reverse-conducting thyristors are used in power electronics as direct-current choppers, converters, uninterruptible power supply systems, electric filters and so forth, (compare the Swiss firm's journal Brown Boveri Mitteilungen 1 (1979), pages 5-10). In all cases in which an inductive load is driven, for example a motor in the field of traction, a current path must be provided in the opposite direction to the conduction direction of the thyristor. A disadvantageous feature of this arrangement is that the turning of of conventional thyristors in self-commutated circuits requires a commutating circuit.
From Hitachi Review, Vol. 31 (1982), No. 1, pages 23-27, it is known to use gate turn-off (GTO) thyristors instead of the conventional thyristors.
GTO thyristors can be obtained with a very wide range of turn-off currents (20 A . . . &gt;2,000 A) and voltages (600 V . . . &gt;4,500 V), (compare IEEE Transaction on Electron Devices, Vol. ED-31, No. 12, December 1984, pages 1681-1686).
If a GTO thyristor is connected in antiparallel with a separate diode, the following problems occur:
the stray inductance of the external circuit leads to overvoltages which can be damaging to the GTO thyristor, PA1 the characteristics of the diode must be matched to the GTO thyristor which can be guaranteed only in a few cases, PA1 the costs are relatively high.